JP2015125869A - Alkaline secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkaline secondary battery having a low risk of malfunction of a valve mechanism which is caused by a molten material clogged in a vent hole upon abnormal situations such as overdischarging or erroneous charging.SOLUTION: A nickel hydrogen secondary battery 1 comprises: an outer can 10 which has an opening at its upper end; an electrode body 20 which is housed in the outer can 10, and around which a positive electrode plate 21 and a negative electrode plate 22 are wound via a separator 23; a sealing plate 31 which seals the opening of the outer can 10; a positive electrode terminal 34 which is electrically connected to the sealing plate 31; and a valve body 33 which opens and closes, in accordance with the pressure inside the outer can 10, a degassing hole 311 formed on the sealing plate 31. The electrode body 20 includes a positive electrode projection 213 with a cylindrical shape which is formed by a portion of the positive electrode plate 21 protruding to the sealing plate 31 side. The positive electrode projection 213 comes into contact with the sealing plate 31 so as to surround the degassing hole 311.

Description

  The present invention relates to an alkaline secondary battery such as a nickel hydride secondary battery.

  A general alkaline secondary battery such as a nickel metal hydride secondary battery has a sealing plate in which an electrode body in which a positive electrode plate and a negative electrode plate are wound via a separator is housed in an outer can and is electrically connected to a positive electrode terminal. And the positive electrode plate of the electrode body are connected by a positive electrode lead (strip-shaped metal member). That is, in the conventional alkaline secondary battery, the positive electrode plate of the electrode body and the positive electrode terminal are electrically connected via the positive electrode lead, and charging / discharging is performed through the positive electrode lead. The conventional alkaline secondary battery having such a configuration has a problem of current collection loss due to contact resistance generated at the connecting portion between the positive electrode lead and the sealing plate. In addition, since the conventional alkaline secondary battery has to place the positive electrode lead in a limited narrow space between the electrode body and the sealing body, the contact area between the positive electrode lead and the sealing plate is structurally limited. It will be. For this reason, the conventional alkaline secondary battery has a certain limitation on the magnitude of the charging / discharging current, which raises the problem that high capacity is hindered.

  As an example of the prior art for solving such a problem, a plurality of convex current collecting plain portions not filled with an active material are formed on the end faces of the positive electrode plate and the negative electrode plate, and the convex shape An alkaline secondary battery in which a current collecting plain part is resistance-welded to a current collecting plate is known (see, for example, Patent Document 1). According to the alkaline secondary battery having such a configuration, a larger charge / discharge current can be flowed, and thus an alkaline secondary battery having a higher capacity than the conventional one can be obtained.

JP-A-8-22818

  By the way, in an alkaline secondary battery, there is a possibility that gas may be abnormally generated inside due to, for example, overdischarge or erroneous charging, and the internal pressure may increase, and the internal pressure may increase due to a normal charge / discharge cycle. Therefore, generally, the alkaline secondary battery is provided with a valve mechanism that opens and closes a vent hole formed in the sealing plate according to the internal pressure of the outer can. More specifically, in the alkaline secondary battery, when the internal pressure of the outer can reaches a certain valve operating pressure, the valve mechanism is opened, and the internal gas is released to the outside through the vent hole. When the internal pressure of the valve decreases, the valve mechanism returns to the closed state. By such a valve mechanism, the internal pressure of the alkaline secondary battery is maintained below a certain pressure.

  However, in the case of an alkaline secondary battery, for example, when overdischarge or erroneous charging occurs, the electrode body may generate heat as the internal pressure increases. In this case, a part of the electrode body (separator or the like) is melted by the heat, and the melted material may be clogged in a vent hole formed in the sealing plate, and the valve mechanism may not operate normally. The amount of the melt produced by melting a part of the electrode body increases as the capacity of the alkaline secondary battery increases. In other words, due to the increase in capacity of alkaline secondary batteries, there is an increased possibility that the valve mechanism will not operate normally due to clogging of the melt into the vent holes when abnormalities such as overdischarge or erroneous charging occur.

  In view of such circumstances, the present invention has been made, and the purpose thereof is an alkaline secondary that is less likely to cause the valve mechanism to not operate normally due to melt being clogged in the vent hole in the event of abnormalities such as overdischarge or erroneous charging. To provide a battery.

<First Aspect of the Present Invention>
According to a first aspect of the present invention, an outer can whose upper end is open, an electrode body accommodated in the outer can and having a positive electrode plate and a negative electrode plate wound through a separator, and an opening of the outer can are sealed. A sealing plate, a positive electrode terminal electrically connected to the sealing plate, and a valve mechanism that opens and closes a vent formed in the sealing plate according to an internal pressure of the outer can. An alkaline secondary battery in which a part of the positive electrode plate includes a cylindrical positive electrode convex portion protruding to the sealing plate side, and the positive electrode convex portion is in contact with the sealing plate so as to surround the vent hole It is.

  In the electrode body, a positive electrode convex portion formed by projecting a part of the positive electrode plate toward the sealing plate is in contact with the sealing plate. As a result, the positive electrode plate of the electrode body is directly connected to the sealing plate, so that a larger charge / discharge current can be passed, and a high-capacity alkaline secondary battery can be realized. The positive electrode convex portion has a cylindrical shape and is in contact with the sealing plate so as to surround the vent hole. Therefore, at the time of abnormality such as overdischarge or erroneous charging, at least the melt generated outside the positive electrode protrusion is prevented from entering the vent by the cylindrical positive electrode protrusion. As a result, it is possible to reduce the possibility that the melt will clog the vent hole and the valve mechanism will not operate normally.

  As a result, according to the first aspect of the present invention, it is possible to provide an alkaline secondary battery in which there is little possibility that the valve mechanism will not operate normally due to the melt being clogged in the vent hole when there is an abnormality such as overdischarge or erroneous charging. The effect that it can be obtained.

<Second Aspect of the Present Invention>
A second aspect of the present invention is an alkaline secondary battery according to the first aspect of the present invention described above, wherein the positive electrode convex portion is formed on the innermost peripheral portion of the positive electrode plate.
According to the second aspect of the present invention, since the melt generated inside the cylindrical positive electrode convex portion can be minimized, the melt is clogged in the vent hole and the valve mechanism does not operate normally. The fear can be further reduced.

<Third Aspect of the Present Invention>
A third aspect of the present invention is the alkaline secondary battery according to the first aspect or the second aspect of the present invention, wherein the positive electrode plate is filled with an active material in a portion other than the positive electrode convex portion. It is.
Since the positive electrode convex portion is not filled with the active material, the gas generated inside the outer can can more easily pass through. As a result, according to the third aspect of the present invention, when the gas generated inside the outer can is discharged to the outside through the vent, it is possible to reduce the possibility that the discharge of the gas is hindered by the positive electrode protrusion. it can.

  According to the present invention, it is possible to provide an alkaline secondary battery that is less likely to cause the valve mechanism to not operate normally due to the melt being clogged in the vent hole when there is an abnormality such as overdischarge or erroneous charging.

The top view which illustrated the longitudinal cross-section of the nickel-hydrogen secondary battery. The perspective view of an electrode body. The top view of a positive electrode core. The top view of a positive electrode plate.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In addition, this invention is not specifically limited to the Example demonstrated below, It cannot be overemphasized that a various deformation | transformation is possible within the range of the invention described in the claim.

<Configuration of nickel metal hydride secondary battery>
The configuration of the nickel metal hydride secondary battery 1 according to the present invention will be described with reference to FIGS.
FIG. 1 is a plan view illustrating a longitudinal section of a nickel metal hydride secondary battery 1. FIG. 2 is a perspective view of the electrode body 20. FIG. 3 is a plan view of the positive electrode core 211. FIG. 4 is a plan view of the positive electrode plate 21.

  A cylindrical nickel-hydrogen secondary battery 1, which is an example of an “alkali secondary battery”, includes an outer can 10, an electrode body 20, and a lid structure 30. The outer can 10 is a bottomed cylindrical member having an open upper end and has conductivity. The electrode body 20 is formed in a substantially cylindrical shape by winding the positive electrode plate 21 and the negative electrode plate 22 in a spiral shape with a separator 23 interposed therebetween. The lid structure 30 is a structure that seals the opening of the outer can 10. The nickel metal hydride secondary battery 1 is configured in such a manner that an electrode body 20 is accommodated in an outer can 10 and further filled with an alkaline electrolyte (not shown), and an opening of the outer can 10 is closed by a lid structure 30. .

  The positive electrode plate 21 is, for example, a non-sintered nickel electrode, and includes a positive electrode core 211 and a positive electrode mixture 212 as an “active material” held by the positive electrode core 211. The positive electrode core 211 is made of a metal material having alkali resistance, for example, and has a felt-like three-dimensional network structure made of metal fibers. As the metal material having alkali resistance, for example, nickel can be used. The positive electrode mixture 212 is used for binding the positive electrode active material particles, various additive particles for improving the characteristics of the positive electrode plate 21, and the mixed particles of these positive electrode active material particles and additive particles to the positive electrode core 211. Consists of a binder.

  The positive electrode active material particles are nickel hydroxide particles. The nickel hydroxide particles may be higher-order nickel hydroxide particles having an average nickel valence of greater than 2. Further, the nickel hydroxide particles may be solid-solved with cobalt, zinc, cadmium or the like, or the surface may be coated with a cobalt compound. As the additive, in addition to yttrium oxide, cobalt compounds such as cobalt oxide, metal cobalt, and cobalt hydroxide, zinc compounds such as metal zinc, zinc oxide, and zinc hydroxide, rare earth compounds such as erbium oxide, and the like can be used. . As the binder, a hydrophilic or hydrophobic polymer or the like can be used. More specifically, the binder may be at least one selected from hydroxypropyl cellulose (HPC), carboxymethyl cellulose (CMC), and sodium polyacrylate (SPA). For example, the binder may be 0.1 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the positive electrode active material particles.

  The negative electrode plate 22 is electrically connected to the outer can 10 while being in contact with the inner peripheral surface of the outer can 10 forming the negative electrode terminal of the nickel-hydrogen secondary battery 1. The negative electrode plate 22 is formed by holding a negative electrode mixture on a conductive negative electrode core (not shown) having a strip shape. The negative electrode core is made of a sheet-like metal material having a plurality of through holes. For example, a punching metal, a metal powder sintered body substrate, an expanded metal, a nickel net, or the like can be used. In particular, a metal powder sintered body substrate obtained by molding punched metal or metal powder and then sintering it is suitable for the negative electrode core.

The negative electrode mixture is composed of hydrogen storage alloy particles capable of occluding and releasing hydrogen and a binder. The hydrogen storage alloy particles may be any particles as long as they can store hydrogen generated electrochemically in an alkaline electrolyte during battery charging and can easily release the stored hydrogen during discharge. Such a hydrogen storage alloy is not particularly limited. For example, an AB ₅ type alloy such as LaNi ₅ or MmNi ₅ (Mm is a misch metal) can be used. Further, the negative electrode mixture may be a cadmium compound, for example, instead of the hydrogen storage alloy. As the binder, for example, a hydrophilic or hydrophobic polymer can be used.

  As the separator 23, for example, a polyamide fiber nonwoven fabric or a polyolefin fiber nonwoven fabric such as polyethylene or polypropylene provided with a hydrophilic functional group can be used as a material.

  The lid structure 30 includes a sealing plate 31, an insulating gasket 32, a valve body 33, and a positive terminal 34.

  The sealing plate 31 is a member that seals the opening of the outer can 10, has a substantially circular shape, and is provided with a circular vent hole 311 as a “vent hole” at the center. The sealing plate 31 is fixed to the outer can 10 by caulking the opening edge of the outer can 10 with the insulating gasket 32 interposed.

  The valve body 33 is a member formed of a material having elasticity such as rubber, and is compressed between the sealing plate 31 and the positive electrode terminal 34 in a state of being in contact with the sealing plate 31 so as to close the gas vent hole 311. It is installed. The valve body 33 functions as a “valve mechanism” that opens and closes the vent hole 311 formed in the sealing plate 31 according to the internal pressure of the outer can 10. More specifically, the valve body 33 is elastically deformed when the internal pressure of the outer can 10 reaches a certain valve operating pressure, whereby the gas vent hole 311 is opened, and the gas inside the outer can 10 passes through the gas vent hole 311. Released. And when the internal pressure of the armored can 10 falls by discharge | release of the gas, the valve body 33 will return to an original shape, and will be in the state which the gas vent hole 311 closed. By such a valve mechanism, the internal pressure of the outer can 10 is maintained below a certain pressure.

  The positive terminal 34 is electrically connected to the sealing plate 31. More specifically, the positive electrode terminal 34 has a cylindrical shape with a flange, and is fixed to the sealing plate 31 so as to cover the valve body 33. In addition, the positive electrode terminal 34 is formed with an exhaust hole 341 for discharging the gas released through the gas vent hole 311 of the sealing plate 31 to the outside.

<Configuration of electrode body 20>
The configuration of the electrode body 20 will be described more specifically with reference to FIGS.

  The electrode body 20 includes a positive electrode convex portion 213 in which a part of the positive electrode plate 21 protrudes toward the sealing plate 31 (FIG. 2). The positive electrode convex portion 213 has a cylindrical shape having a diameter larger than that of the vent hole 311 of the sealing plate 31 and is in contact with the sealing plate 31 so as to surround the vent hole 311 of the sealing plate 31 (FIG. 1).

  In the nickel metal hydride secondary battery 1 provided with such a positive electrode convex portion 213, the positive electrode convex portion 213 is in contact with the sealing plate 31. That is, in the nickel metal hydride secondary battery 1, since the positive electrode plate 21 of the electrode body 20 is directly connected to the sealing plate 31, a larger charge / discharge current can flow. Thereby, a high-capacity nickel metal hydride secondary battery 1 can be realized. In addition, since it is not necessary to perform resistance welding or the like as in the prior art, the manufacturing process of the nickel metal hydride secondary battery 1 can be simplified.

  The positive electrode convex portion 213 is in contact with the sealing plate 31 so as to surround the gas vent hole 311 of the sealing plate 31. Therefore, when the nickel hydride secondary battery 1 is abnormal such as overdischarge or erroneous charging, at least the melt generated outside the positive electrode protrusion 213 is prevented from entering the gas vent 311 by the cylindrical positive electrode protrusion 213. Will be. On the other hand, since the positive electrode core 211 constituting the positive electrode convex portion 213 has a felt-like three-dimensional network structure made of metal fibers, the gas generated inside the outer can 10 causes the positive electrode convex portion 213 to flow. It passes through and is discharged to the outside through the vent hole 311. In this way, when the nickel hydride secondary battery 1 is abnormal, such as overdischarge or erroneous charging, it is possible to reduce the possibility that the melted material clogs the gas vent hole 311 and the valve element 33 does not operate normally.

  In the present invention, the positive electrode convex portion 213 is preferably formed on the innermost peripheral portion of the positive electrode plate 21. As a result, the melt generated on the inside of the cylindrical positive electrode convex portion 213 can be minimized, thereby further reducing the possibility that the melt will clog the degassing hole 311 and the valve element 33 will not operate normally. be able to. In the present invention, it is preferable that the positive electrode convex portion 213 is filled with an active material in a portion other than the positive electrode convex portion 213. That is, it is preferable that the portion of the positive electrode plate 21 where the positive electrode convex portion 213 is formed is not filled with the active material. Accordingly, the gas generated inside the outer can 10 can more easily pass through the positive electrode convex portion 213, so that when the gas generated inside the outer can 10 is discharged to the outside through the gas vent 311, the gas Can be prevented from being hindered by the positive electrode convex portion 213.

  The positive electrode convex portion 213 of the electrode body 20 can also be used to support the lid structure 30 in the manufacturing process of the nickel metal hydride secondary battery 1. More specifically, in the manufacturing process of the nickel metal hydride secondary battery 1, the positive electrode convex portion 213 of the electrode body 20 is brought into contact with the sealing plate 31 and the positive electrode convex portion 213 supports the lid structure 30. The opening edge of the outer can 10 can be caulked. Accordingly, the lid structure 30 can be fixed to the outer can 10 in a state where the positive electrode convex portion 213 of the electrode body 20 is in contact with the sealing plate 31.

  The electrode body 20 including the positive electrode convex portion 213 as described above can be manufactured as follows, for example.

  First, the positive electrode core body 211 in which the convex portion to be the positive electrode convex portion 213 is formed on the winding start side 214 is manufactured (FIG. 3). The width of the convex portion that becomes the positive electrode convex portion 213 is a cylinder that surrounds the gas vent hole 311 of the sealing plate 31 by slightly overlapping both ends of the convex portion when the electrode body 20 is wound up. The width is preferably such that the positive electrode convex portion 213 is formed. Further, the height of the convex portion that becomes the positive electrode convex portion 213 may be a height at which the upper end of the positive electrode convex portion 213 contacts the sealing plate 31 when the nickel-hydrogen secondary battery 1 is configured. Moreover, since the positive electrode core body 211 of the positive electrode plate 21 has a felt-like three-dimensional network structure made of metal fibers as described above, it has elasticity. Therefore, if the height of the convex portion that becomes the positive electrode convex portion 213 is set slightly longer, the positive electrode convex portion 213 is pressed against the sealing plate 31, and the contact area of the positive electrode convex portion 213 with respect to the sealing plate 31 becomes larger. Therefore, it is preferable.

  Subsequently, the positive electrode mixture 212 is applied to both surfaces of the positive electrode core 211 other than the convex portion that becomes the positive electrode convex portion 213 (FIG. 4). Then, as described above, the positive electrode plate 21 and the negative electrode plate 22 are overlapped via the separator 23 and wound in a spiral shape. Thus, the electrode body 20 including the cylindrical positive electrode convex portion 213 formed by projecting a part of the positive electrode plate 21 toward the sealing plate 31 can be configured.

DESCRIPTION OF SYMBOLS 1 Nickel metal hydride secondary battery 10 Outer can 20 Electrode body 21 Positive electrode plate 22 Negative electrode plate 23 Separator 30 Lid structure 31 Sealing plate 32 Insulating gasket 33 Valve body 34 Positive electrode terminal

Claims (3)

An outer can with an open top;
An electrode body housed in the outer can, and a positive electrode plate and a negative electrode plate wound around a separator;
A sealing plate for sealing the opening of the outer can;
A positive terminal electrically connected to the sealing plate;
A valve mechanism for opening and closing the vent hole formed in the sealing plate according to the internal pressure of the outer can,
The electrode body includes a cylindrical positive electrode convex portion in which a part of the positive electrode plate protrudes toward the sealing plate, and the positive electrode convex portion is in contact with the sealing plate so as to surround the vent hole. Alkaline secondary battery.   The alkaline secondary battery according to claim 1, wherein the positive electrode convex portion is formed on an innermost peripheral portion of the positive electrode plate.   3. The alkaline secondary battery according to claim 1, wherein the positive electrode plate is filled with an active material in a portion other than the positive electrode convex portion. 4.

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